1. Field
Embodiments of the invention relate to the field of mobile IP (Internet Protocol); and more specifically, to a virtual care-of address assigned to a mobile node.
2. Background
Mobile IP is a protocol described in Request for Comments (RFC) 3344, August 2002, which allows laptop computers or other mobile computing units (referred to as mobile nodes herein) to roam between various sub-networks at various locations, while maintaining Internet and/or WAN connectivity. Mobility agents (e.g., home agent, foreign agent) provide Mobile IP functionality. In a typical Mobile IP network, each mobile node is identified by its home address (assigned by a home agent), regardless of its current point of attachment to the Internet. While situated away from its home, a mobile node is also associated with a care-of address (provided by a foreign agent), which indicates its current point of attachment for reachability. While a mobile node is away from its home and connected to a foreign network it requests registration through the foreign agent to the home agent. If the registration is successful, when the mobile node's home network receives packets addressed to the mobile node, the home agent will send those packets, over a tunnel, to the foreign agent which in turns forwards the packets to the mobile node. When the mobile node is sending packets, the foreign agent may employ reverse-tunneling and send the packets to the home agent who in turn forwards the packets to their destination, or the foreign agent may directly forward the packets to their destinations. When the mobile node is successfully registered, the mobile node has started a Mobile IP session. When the mobile node is deregistered (e.g., the bindings for the mobile node have been removed), the Mobile IP session has ended. The tunnel used between home and foreign agents can be IP-IP or GRE as described in RFC 3344.
FIG. 1 presents a sample illustration of the prior art in the field of mobile IP. Mobile node 105 is granted an IP session by way of foreign agent 120 and home agent 130. Foreign agent 120 and home agent 130 can act as routers. In particular, mobile node 105 is coupled to foreign agent 120 through a base station or distributed access point 115. As shown in FIG. 1, a foreign agent address “FAA” is utilized between access point 115 and foreign agent 120. Another mobile node 110 can also be coupled to foreign agent 120 through the same base station 115. Foreign agent 120 serves as the local point of attachment for its coupled to mobile nodes 105, 110. The foreign agent 120 is coupled to a home agent 130 that provides IP connectivity 135, 140 (Internet and corresponding node). In other words, home agent 130 supports IP sessions for mobile nodes 105, 110 through foreign agent 120 and base station 115.
In FIG. 1, foreign agent 120 and home agent 130 are connected by one tunnel serviced by an ISP (Internet Service Provider) 125. The terminating point of the tunnel ending at foreign agent 120 is denoted by a care-of address (CoA) and the other terminating point of the tunnel ending at home agent 130 is denoted by a home agent address (HAA). A CoA is an address of a foreign agent with which a mobile node is registered. In this example, foreign agent 120 only has one CoA. Since mobile nodes 105, 110 had selected the CoA of this foreign agent 120 for their IP sessions, traffic for mobile nodes 105, 110 are directed through this tunnel. Here, there is only one tunnel between foreign agent 120 and home agent 130 by which to carry traffic for IP sessions.
In another example, more than one tunnel can exist between foreign agent 120 and home agent 130. Each of the tunnels can have a different CoA at their foreign agent 120 endpoints. In this situation, mobile nodes 105, 110 each select one of the CoAs at random. It can be the same CoA or two different CoAs. The tunnel used to carry traffic for the IP session of the mobile node is the tunnel attached to the CoA selected by the mobile node. Therefore, the particular tunnel that supports an IP session for a node is dependent on the mobile node's random selection of a CoA. However, the tunnel used can encounter various problems such as overloading or unreliable service from an ISP. Measures are not in place to avoid or remedy the problems that arise in these circumstances.
Interrupting IP connectivity to a mobile node is inconvenient for a mobile node user who relies on his communications device to conduct business, obtain information, etc. Thus, enhancing reliability of IP connectivity for a mobile node is desirable for the user.